Fri Jun 24 16:23:01 2005  George Lebl <jirka@5z.com>

	* src/longtest.gel: add many derivative tests

	* src/funclib.c: add IsFunctionOrIdentifier

	* lib/calculus/differentiation.gel: accept identifiers for all
	  functions and not just functions

	* help/C/gel-function-list.xml: add IsFunctionOrIdentifier

	* src/eval.c: Allow identifier + string to make a string

	* src/symbolic.c: fix some derivative definitions

	* src/eval.c: fixup nargs when creating new operator nodes in
	  simplification